CV joints are typically employed in automotive axial drive shafts, and especially in front-wheel-drive vehicles between the transaxle differential and the driving wheel. The CV joints transmit a torque at various speeds, angles and telescopic positions between a first shaft and a second shaft.
Current developments in the field of CV joints are generally directed toward improving performance of these CV joints, such as by increasing their torque transmitting capability and reducing their noise and vibration. It is also necessary to provide sealing of the various joint configurations developed to ensure their performance and provide desirable protection in their operating environments.
It is desirable to seal the CV joints described above with a boot to prevent dirt and debris from entering and damaging the components of the CV joint. Such boots are often manufactured from thermoplastic materials for many reasons, including their cost and ability to provide the desired protection for the CV joints over their operating lifetimes. However, any boot utilized must permit passage of the larger diameter portions, such as their ends which comprise portions of the CV joint, therethrough, while also providing sealing against the smaller diameter of the axle portion of the associated shaft. The thermoplastic boots typically utilized, while sufficiently flexible for the intended use, are relatively inelastic, i.e., the thermoplastic boots typically utilized are not capable of expanding or stretching to permit passage of the larger diameter portions therethrough and also sealing against the smaller diameter axle portions. Therefore, it is desirable to provide CV joints having thermoplastic boots which are capable of providing the necessary joint protection, but which are also capable of providing design flexibility for installation over certain portions of the joints that have enlarged diameters, while also providing sealing on relatively smaller diameter portions, such the joint shafts.